Impulse-repeating device for automatic and semiautomatic telephoneexchange systems



July 9, 1929. R c cg sK 1.720.107

IMPULSE REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEMS I Filed March 1927 5 Sheets-Sheet l R Ohm g mama July 9, 1929. TREHc|N$K| 1.720.107

IMPULSE REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEMS Filed March 3, 1927 5 Sheets-Sheet 2 v lllll R. 7710A chasm INVENTOK July 9, 2 R. TRECHCINSKI 1.720.107

IMPULSE REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEMS Filed March 3, 1927 5 Sheets-Sheet Q a T [N J 5 I N n/ .v. m a A m r 7 [(I 9 6 w Q N. a l 1% R R L July 9, 1929. R c N5 1.720107 7 IMPULSE REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEMS Filed March 1927 5 Sheets-Sheet 4 July 9. 1929 R. TRECHCINSKI IMPULSE REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEMS Filed March 3, 1927 5 Sheets-Sheet l atented July 9, 1929 UNITED STATES PATENT OFFICE.

ROMAN TRECHCINSKI, 0F WARSAW, POLAND, ASSIGNOR TO TELEFONAKTIEBOLAGET L. M. ERICSSON, OF STOCKHOLH, SWEDEN, A COMPANY 01' SWEDEN.

IMPULSE-REPEATING DEVICE FOR AUTOMATIC AND SEMIAUTOKATIC TELEPHONE EXCHANGE SYSTEMS.

Application filed larch 3, 1927, Serial No. 172,489, and in Poland larch 9, 1988.

The invention relates to impulse repeating devices for automatic and semi-automatic telephone exchange systems and is particularly contemplated for use in telephone plants in which the len 'ths of the subscribers lines vary considerabl y, as for instance in rural plants. The object of the invention is to provide a reliable impulse repeating device the operation of which is not affected by the varying length and resistance of the lines over which the impulses are sent.

According to the invention the winding of the impulse receiving relay is connected through voltage reducing resistances to the source of current of the sending line in such a way that, upon opening the line circuit or increasing the resistance thereof to a certain extent, the energizing current of the impulse relay will increase to an amount sufficient to operate the relay. In such an arrangement the operation of the impulse relay will evidentlv be independent of the length and resistance of the line. In carrying out the invention a circuit arrangement of the bridge connection type is preferably used which is so balanced that the winding of the impulse relay will be currentless at a predetermined resistance of the sending line, for instance, at a resistance of about the average resistance of the lines in question. Such a circuit arrangement, which provides a very sensitive impulse repeating device, has also other advantages as will appear from the following description.

The invention will be more closely described with reference to the accompanying drawings which show different forms of the circuit arrangement of the kind referred to.

Figure 1 is a circuit diagram illustrating the principle of the invention. Figure 2 is a diagram explainin the operation of the circuit arrangement s hown in Figure 1. Figures 3 and 4 show different circuit arrangements for a polarized impulse relay. F igure 5 shows an arrangement for connecting the impulse relay and the appertaining voltage reducing device to a talking line. Fig ure 6 shows a modification of the circuit arrangement last mentioned. Figure 7 is a corresponding circuit arrangement for a nonpolarized impulse relay.

In Figure 1 a subscribers instrument 1 is connected to the central exchange throu h a line 2 and arranged to receive microp one current in the usual way through choking coils 3, 4 from a central battery 5. Branched off from the line terminals 6, 7 is a shunt including the winding 8 of the impulse relay and an auxiliary. source of current 9. In practice the impulse rela 8 is not assigned individually to a subscri ers line but associated with a junction line in the exchange and adapted to be connected to the calling subscribers line by some automatic switchin means. The auxiliary source of current 9 has a lower voltage than the central battery 5. The amount of voltage between the terminals 6 and 7 evidentl depends upon the total resistance R of the inc 2 and the telephone instrument 1. The voltage will approach zero when a very short line is connected up and will assume a maximum value upon the opening of the line circuit, said maximum value bein greater than the Volta e of the auxiliary battery. The current 2, in the shunt will flow, as occasion requires, either in the direction shown in Figure 1, which may be called the positive direction, or in the opposite negative direction, or, contingently, no current will flow through the shunt.

It may be assumed that the direct current resistance of each of the windings 3 and 4 is 150 ohm and that of the windings 8 is 300 ohm. The terminal voltage of the central battery 5 and the auxiliary battery 9 are assumed to be 24 and 18 volt respectively. Under these circumstances the energizi current i, of the impulse relay will vary wit the total resistance of the line 1, 2 in the way illustrated by the diagram in Figure 2. The current i, has its greatest negative value for R=0. For R=900 ohm the current will be 0. On a further increase of the resistance R the current will approach its greatest positive value of 10 milliampere which is attained when the line circuit 2 is open. The strength of the current 'Z,+z' passing through the choking coils 3, 4 will decrease with the increasing resistance R and will also approach a limit Value of 10 milliampere. If these choking coils consist of windings of relays which are to be kept energized during the impulse sendback contact.

ing, said relays must evidently be so devised as to keep their armatures attracted even at that limit value of the current.

At first it may be assumed that the impulse relay 8 is a polarized relay. In the arrangement shown such a relay should be adjusted, by setting the magnet poles or in any other way, so that the armature will rest on its back contact when the relay is currentless as well as when it is energized by a negative current. The sensitiveness must evidently be sufiicient to cause the relay to operate by a positive current of 10 milliampere. A decrease of the resistance R, for instance by short-circuiting the telephone instrument 1, will have no other effect on the impulse relay than to keep the armature pressed more firmly against the The impulserelay may thus be caused to operate either by opening the line circuit 2 or by increasing the resistance thereof to such an amount that the energizing current of the impulse relay approaches its positive limit value. Both said means are, as will appear from Figure 2, practically equivalent. The operation of the impulse relay may be brought about either by repeated interruptions of the line circuit during the impulse sending or by the restoring of the microtelephone on its support on the telephone instrument. The movements of the relay armature caused by the said repeated interruptions of the line circuit are utilized in known manner to control a local circuit for the setting of a selector switcln In operating the impulse relay by interruptions of the line circuit the operating current ofthe relay amounts, in the example stated, to 10 milliampere. In case the relay is operated by introducing a great resistance sufiicient to operate the relay. If the line is soshort that its resistance is less than R the relay will be operated whether the line circuit isinterrupted or not, and, as a consequence, it cannot be used for such a llne. On the other hand, this feature of the non-polarized relay,

in this combination may be utilized to disable certain subscribers lines from using certain junction lines; This form of the invention may for instance be applied with advantage in private branch exchanges for preventing some of the telephone instruments connected to this exchange to have access to trunk lines leading to the main exchange.

As already mentioned it is not necessary to interrupt the impulse circuit completely for each impulse but instead thereof a great resistance may be introduced in the circuit with practically the same efi'ect.

In the circuit arrangement shown in Figure 3 the impulse relay 8-is connected up in the same way as in Figure 1 and is, consequently, connected to the terminals 6, 7 in series with the auxiliary source of current 9. Figure 3 shows in connection therewith a line 10 Over which the impulses produced b y the impulse relay are sent further on. The line 10 may consist of a unction line in the local exchange leading to a selective switch, or it may be a trunk line leading to another exchange. The

line 10 is connected with the line 2 through a talking current transformer 11 the primary winding of which is connected over the condenser 12 to the terminals 6, 7. The line circuit 10 includes the back contact 13 of the impulse relay 8 and is therefore closed when the relay armature 14 takes up the normal position shown in Figure 3. Upon interruption of the line circuit 2 the armature is shifted to make contact with the contact 15, whereby the line circuit 10 is opened.

The circuit arrangement according to Figure 4. differs from the arrangement just described only by the fact that no separate auxiliary source of current is used. Instead thereof the circuit of the impulse relay 8' includes part of a voltage reducing device or potentiometer 26 connected directly to the central battery 5. This circuit arrangement will evidently operate in the same way as that shown in Figure 3.

Figure 5 shows those parts of the circuit arrangement of Figure 4 which are lying on the other side of the terminals 6, 7 and includes certain switching relays by means of which the impulse relay PR is connected up to the terminals 6, 7 upon a call occurring. The nature of the arrangement will appear from the following description of the operation.

After the subscribers line has been connected in known manner by" a re-selecting operation to the junction line L a switching relay RR, the winding of which is connected up between the terminal 6 and the plus-pole of the central battery in series with the middle contact 16 of an auxiliary relay HR and a contact 17 of a slow-act ing relay VB, will receive energizing current from the central battery. Said relay, upon energizing, closes the circuit of the auxiliary relay HR at the contact 18. Relay HR, upon energizing, opens at 16 the circuit of the relay RR which then releases its arma-.

ture and opens the contact 18. Relay HR, however, has connected itself, by the closure of the contact 19, in a retaining circuit over contactl7, and at the same time it has closed at its contact 20, the circuitof a relay ER,

which now will close live different spring contacts 21-25. The two lowermost contacts 21, 22 will connect the end points of the voltage reducing device 26 with the terminals of the'central battery. The next two contacts 23, 24 will connect up the impulse relay PR to the terminals 6, 7 and the uppermost contact 25 will connect up the line 10. The impulse repeating operation may now begin. Upon each interruption of the line circuit 2 the armature of the impulse relay is shifted against the contact 15, whereby the winding of the slow-acting re lay VB is connected to the line it) in series with a choking coil S5. The impulses are too short to operate the slow-acting relay VR but the great resistance of the windings VR and Si will have the same effect as an interruption of the line 10. By the impulses thus transmitted the selector switch connected up to the line 10 at the other end thereof will be operated.

Upon the micro-telephone being restored on the telephone instrument at the end of the conversation, the armature 14 of the i1npulse relay PR is shifted against the contact 15 on account of the interruption of the line circuit 2, the slow-acting relay VR being thereby supplied with current for a suffieient length of time to enable it to attract its armature. The circuits of the relays HR and ER will thus be opened at 17. e impulse relay will be de-energized by the interruptions at the contacts 23, 24 so that its armature is caused to bear against the contact 13. As a conseqcence, the slow-acting relay will also deenergize.

The circuit arrangement according to Figure 6 differs from that ust described principally only by the fact that the auxiliary relay HR is dispensed with. The relay RR will in this case switch the relay ER directly into circuit and will remain operated during the selective operation and during the conversation. In addition, a choking coil Si is connected into the circuit of the impulse relay PR.

In the circuit arrangement according to Figure 7 a non-polarized relay IR is used instead of the polarized relay. Otherwise the circuit arrangement is the same as in Figure 6. The special advantages of using a non-polarized relay in this combination is already mentioned.

In using the arrangements described for sending of impulses over trunk lines extending between different exchanges the advantages are the same as in sending of impulses over subscribers lines, inasmuch as the operation of the impulse relay is independent of the length and resistance of the trunk lines.

I claim:

1. A circuit arrangement for transmitting current impulses over telephone lines comprising a line circuit including a central hattery, a local circuit including an impulse repeating relay, said circuits being interconnected so as to form a circuit combination of the bridge connection type, means for producing current impulses in the line circuit, and means included in said circuits and adapted to cause an increase of current in the local circuit upon an increase of the resist ance of the line circuit.

2. A circuit arrangement for transmitting current impulses over telephone lines comprising a line circuit including a central battery, a local circuit including an impulse rcpeating relay said circuits being interconnected so as to form a circuit combination of the bridge connection type, means for interrupting the line circuit and means included in said circuits and adapted to cause an increase of current in the local circuit upon each interruption of the line circuit.

3. A circuit arrangement as claimed in claim 1, in which the circuits are balanced so as to send no current through the impulse relay for a predetermined value of the resistance of the line circuit.

4. A circuit arrangement as claimed in claim 1 in which the winding of the impulse relay is connected to the central. battery, through voltage reducing resistances.

5. A circuit arrangement for transmitting current impulses over telephone lines comprising a line circuit including a central battery, voltage reducing resistances connected between said battery and the line branches, means for producing current impulses in the line circuit and an impulse relay shunted to the line in series with an auxiliary source of, current.

6. A circuit arrangement as claimed in claim 5 in which the voltage reducing resistances consist of choking coils.

7. A circuit arrangement for transmitting current impulses over telephone lines comprising a line circuit including a central battery, voltage reducing resistances connected between said battery and the line branches, means for producing current impulses in the line circuit and a local circuit including said central-battery, said voltage reducing resistances, an impulse relay and a counteracting auxiliary source of current connected in series.

8. A circuit arrangement as claimed in claim 7, in which the auxiliary source of current consists of a potentiometer shunted to the central battery.

9. A circuit arrangement as claimed in claim 7, in which the line circuit and the local circuit are balanced so as to cause the operating current of the impulse relay to change di' rection for each impulse in the line circuit.

10. A circuit arrangement as claimed in claim 7, in which the impulse relay consists of a polarized relay, the line circuit and the local circuit being balanced so as to cause the operating Current of the impulse relay to change direction at a predetermined value of the resistance of the line circuit.

11. A telephone exchange system comprising a number of subscribers lines, a number of junction lines, means for establishing connections between said subscribers lines and junction lines, a central battery, choking coils connected between the battery and the junction line branches and a local impulse circuit comprising said central battery, sa d Choking coils, an impulse relay and a counteracting auxiliary source of current connected in series.

12. A telephone exchange system as claimed in claim 11 in which the impulse re lay consists of a neutral relay and in which certain subscribers lines are precluded from using said junction lines by being given a resistance which is loW enough to cause the impulse relay to be operated by an interruption of the line circuit as Well as by the normal closure of said circuit.

In testimony whereof I aiiix my signature.

ROMAN TRECHCINSKI. 

